The ultrastructure of tumours derived from spontaneously transformed tissue culture cells.

The ultrastructure of 16 tumours derived from spontaneously transformed cell lines established from young and old C57 and C3H mouse organs is described. Three types of tumour were found: myxoid (fibrosarcomatous), consisting of cells with long processes and much interstitial material; leiomyomatous, consisting of a bundle of smooth muscle-like cells with less interstitial material; or epithelial-like consisting of closely packed round cells with little interstitial material. The cell types in the tumours were similar to those found in the tissue culture cell lines from which they were derived.